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                                        <p>But it was in the late 70's when Davies concentrated his work on data security. In 1979 realizing that computer networks would be used widely only if malicious interference could be prevented, Davies formed a Data Security group under his leadership, at NPL, UK.</p>
                                        <h2>How did the group start?</h2>
                                        The group started to work on data security mainly concentrating on the new method of public key cryptosystems. The first task of the new Data Security group was to familiarize itself with computer cryptography of that time. There were two recent important developments.
                                        <ol>
                                            <li><strong>Data Encryption Standard (DES):</strong><br>
                                                <span>The first was the publication in January 1977 of a Data Encryption Standard (DES) by the US National Bureau of Standards. Its main features were:</span>
                                                <ul>
                                                    <li>Fully public</li>
                                                    <li>Couldn't be broken</li>
                                                    <li>Encryption and decryption algorithms were closely similar</li>
                                                    <li>Key couldn't be known even when original text and encrypted text were known</li>
                                                </ul>
                                                <br>																				
                                            </li>
                                            <li><strong>Public key cryptosystems:</strong>
                                            <br><span>The other, also American, was the invention of public key cryptosystems. In this system, each participant in the communication has a unique pair of key; a <i>private key</i>, which must be kept secret and <i>public key</i> that is published to all concerned. To send a message, the message is encrypted with a recipient's public key which cannot be decrypted by anyone except the recipient possessing the corresponding private key.
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                    <div id="bottombackground">References.
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                            <li>[1] David M Yates, <strong>Turing's Legacy</strong>, published by Science Museum London</li>
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